In this paper we explore the relations among advertising spending, capacity and quality for services. Data from a sample of New York City restaurants show that mid-quality restaurants spend more on advertising than either high quality or low quality ones, contradicting the usual Nelson-type prediction that advertising spending increases with quality. Also, controlling for quality, restaurants with larger capacities advertise more. We present a model of services to explain these observations. The key features of the model are: (1) capacity constraints, (2) uncertain demand, (3) the presence of both informed and uninformed consumers, and (4) a technological link between capacity and quality. We argue that for services, advertising not only informs consumers, but it also can improve capacity utilization. Given this dual role, advertising is more valuable to firms with larger capacities and higher price-cost margins. The variation of these two elements with quality determines the advertising-quality relation.